1. Technical Field
The embodiments herein generally relate to an analog electronics system that integrates to a standoff detection sensor for detecting chemical and biological materials at a distance, and, more particularly, to an analog electronics system that measures elements of the Mueller matrix at infrared CO2 laser wavelengths from a photopolarimetric-based sensor apparatus, and preprocesses those data fields so as to identify targeted contaminants—such as biological aerosol and liquid chemical warfare agents or simulants of such compounds—by their unique polarized infrared elastic backscattering signatures brought out in a differential-absorption Mueller matrix spectroscopy (DIAMMS) operation mode of sensor.
2. Description of the Related Art
A variety of systems and methods have been developed and used to detect and identify hazardous chemical and biological threat agents in the field. Passive infrared (PIR) imaging sensors detect airborne chemical threats such as nerve (GA, GB, and GD) and blister (H and L) agents based on the infrared spectrum of the agent. Currently, fielded devices have been reported to detect aerosols at a distance of up to 5 km. Practical PIR detection systems generally have difficulty detecting low levels of chemical-biological warfare (CBW) surface target contaminants because the surfaces are typically at thermal- or pseudo-equilibrium and provide insufficient contrast to identify target contaminants. U.S. Pat. Nos. 5,241,179; 6,464,392; 6,731,804; and 7,262,414, the complete disclosures of which, in their entireties, are herein incorporated by reference, address this issue by externally stimulating the subject target contaminant/background with radiation to produce sufficient contrast when performing detection functions.
Additionally, background radiation and interference encountered in the field can mask the infrared signature of contaminant, making the detection event difficult if not impossible. Uniqueness of detection is, furthermore, a major issue with PIR detection systems as they typically rely on one quantifier; i.e., the infrared signature spectrum.
What is needed in a standoff detection system is technology that provides a truly unique metric for revealing an analytic contaminant (i.e., chemical and biological, or chemical/biological (CB), warfare agents) that can be measured in the field rapidly, reliably, and repeatedly at very low concentration levels of that analyte. The sensor built around this technology must operate remotely at a safe distance in order to detect target contaminants before casualty-producing concentrations are encountered.